On the 140 the job is a "dash out", not partially but totally. I would not let anyone who has not done the job at least once at it. The newer "evap" is smaller and needs a filler panel. My local MB dealer does not let anyone do it, 3/4K is a pretty good price mine was 2k and they split the cost of the parts and labor. they also replaced the dryer, some questinable hoses some sensors and other items.
Just remember when they are in there it is easy for the mechanic to go to the parts counter, and ask his buddies for advice and help.
Can it be done yes, labels, pictures, and a lot of time. The carbon filter is under the windshield wiper mechanism.